1960. There's an outbreak of smallpox in Moscow. This incurable deadly disease was considered conquered in the USSR. To fight the possible epidemic the KGB assigns colonel Shilov. He dives into the struggle at once because he has an old account to settle with smallpox. The task is to locate all those infected and stop the spread of the virus. But it is not an easy mission. The infection has spread to the underworld of the capital. Shilov must look for answers in the depths of the criminal world, unearthing its inhabitants and secrets.